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Issue 29, 2020

Correlative cathodoluminescence electron microscopy bioimaging: towards single protein labelling with ultrastructural context

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Abstract

The understanding of living systems and their building blocks relies heavily on the assessment of structure–function relationships at the nanoscale. Ever since the development of the first optical microscope, the reliance of scientists across disciplines on microscopy has increased. The development of the first electron microscope and with it the access to information at the nanoscale has prompted numerous disruptive discoveries. While fluorescence imaging allows identification of specific entities based on the labelling with fluorophores, the unlabelled constituents of the samples remain invisible. In electron microscopy on the other hand, structures can be comprehensively visualized based on their distinct electron density and geometry. Although electron microscopy is a powerful tool, it does not implicitly provide information on the location and activity of specific organic molecules. While correlative light and electron microscopy techniques have attempted to unify the two modalities, the resolution mismatch between the two data sets poses major challenges. Recent developments in optical super resolution microscopy enable high resolution correlative light and electron microscopy, however, with considerable constraints due to sample preparation requirements. Labelling of specific structures directly for electron microscopy using small gold nanoparticles (i.e. immunogold) has been used extensively. However, identification of specific entities solely based on electron contrast, and the differentiation from endogenous dense granules, remains challenging. Recently, the use of correlative cathodoluminescence electron microscopy (CCLEM) imaging based on luminescent inorganic nanocrystals has been proposed. While nanometric resolution can be reached for both the electron and the optical signal, high energy electron beams are potentially damaging to the sample. In this review, we discuss the opportunities of (volumetric) multi-color single protein labelling based on correlative cathodoluminescence electron microscopy, and its prospective impact on biomedical research in general. We elaborate on the potential challenges of correlative cathodoluminescence electron microscopy-based bioimaging and benchmark CCLEM against alternative high-resolution correlative imaging techniques.

Graphical abstract: Correlative cathodoluminescence electron microscopy bioimaging: towards single protein labelling with ultrastructural context

Article information


Submitted
31 Mar 2020
Accepted
08 Jul 2020
First published
10 Jul 2020

This article is Open Access

Nanoscale, 2020,12, 15588-15603
Article type
Minireview

Correlative cathodoluminescence electron microscopy bioimaging: towards single protein labelling with ultrastructural context

K. Keevend, T. Coenen and I. K. Herrmann, Nanoscale, 2020, 12, 15588 DOI: 10.1039/D0NR02563A

This article is licensed under a Creative Commons Attribution 3.0 Unported Licence. You can use material from this article in other publications without requesting further permissions from the RSC, provided that the correct acknowledgement is given.

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